How do you determine if a element/ion is an isotope(yes or no). For example, the question 39K
19
19 is the atomic number. I did my best to write it.

2.00 is the !

Hi + naoh -> h2o + nal

Answer:             1.0  × 10⁻⁵ msolution:                     as we know ph is given as,                                    ph  = -log [h⁺]and,                                    [h⁺]  =  10^-ph    (1)putting value of ph in eq. 1,                                    [h⁺]  =  10⁻⁵                                    [h⁺]  =  1.0  × 10⁻⁵ m

The answer is a. mars